Antikythera Mechanism

The largest fragment of the Antikythera Mechanism is on display at the National Archaeological Museum of Athens. The device was constructed sometime between 150 and 100 BC, and was used for astronomical calculations.

Jo Marchant / Nature.

Given that the ancient Greeks established the foundation of Western civilization, it's hard to overstate their significance in world history. But according to a newly published study of a Greek astronomical computing device built between 150 and 100 BC, they were even more technologically advanced than classical scholars have realized.

The device, made of bronze and encased in wood, was found by divers off the Mediterranean island Antikythera in 1900. Scientists have studied the so-called Antikythera Mechanism for decades, but in paper published in the November 30th Nature, an international team led by Mike Edmunds and Tony Freeth (Cardiff University, Wales) report detailed studies using high-tech tools. Three-dimensional X-ray tomography enabled the scientists to count individual teeth in at least 30 precision, hand-cut gears. The group also conducted high-resolution surface imaging of many of its 80 fragments, which allowed the scientists to decipher new Greek inscriptions.

With this new information, the team could reconstruct the Antikythera Mechanism's functions. The device enabled astronomers in the second century BC to predict the movements of the Moon and Sun, along with lunar and solar eclipses. It could recreate irregularities in the Moon's motion due to its elliptical orbit. And it may have even enabled Greek astronomers to forecast the positions of the known planets.

"This device is just extraordinary, the only thing of its kind," says Edmunds. "The design is beautiful. The astronomy is exactly right. The way the mechanics are designed just makes your jaw drop."

Astronomer and historian Bradley Schaefer (Louisiana State University), who was not a member of the team, comments, "This is all rather exciting, as it shows a greatly more sophisticated technology for the Greeks than any had really imagined. And this technology is far in advance of anything else for almost a millennium."

British science historian Derek de Solla Price first suggested in the 1950s that the mechanism is an analog computer for astronomical calculations, a conclusion bolstered by subsequent analysis. But because the device is corroded and fragmented, this theory was not completely proved until this new study. "The X-ray tomography is a neat idea to see the inside guts of the corroded remains and see the details of the gears and to see new inscriptions," says Schaefer. "With the gear works and the inscriptions, the idea that it is an astronomical orrery is now irrefutable."

The international team hopes to produce a full working replica of the Antikythera Mechanism, which is stored at the National Archaeological Museum of Athens in climate-controlled conditions. Nobody knows whether it was a one-of-a-kind device, or if there are similar machines waiting to be unearthed. "It does raise the question what else were they making at the time," says Edmunds. "In terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa."


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